302 THE FUNGI WHICH CAUSE PLANT DISEASE 



Key to Families of Ustilaginales 



Promycelium usually with sporidia lateral 



at septa 1- UstUaginacese, p. 302. 



Promycelium with clustered terminal 



sporidia 2. Tilletiacese, p. 314. 



Ustilaginaceae 



Sori usually forming exposed dusty or agglutinated spore- 

 masses. Germination of chlamydospores by means of septate 

 promycelia which give rise to terminal and lateral sporidia or else 

 to infection-threads. 



Key to Genera of Ustilaginacece 



Spores single 



Sori dusty at maturity 



Without definite false membrane 1. TTstilago, p. 303. 



With false membrane of definite fungous 



cells 2. Sphacelotheca, p. 310. 



Sori agglutinated at maturity 

 Firmly agglutinated into conspicuous 



tubercular nodules 3. Melanopsichium. 



Developed around a central columella 



(rarely dusty) 4. Cintractia. 



Spores cluefly in pairs 



Sori agglutinated (on leaves) 5. Schizonella. 



Sori dusty (inside peduncles) 6. Mykosyrinz. 



Spores in balls of more than two 

 Sori dusty or granular 

 Spore-baUs often evanescent; spores 



olive-brown or black-brown 7. Sorosporium, p. 312. 



Spore-balls rather permanent; spores 

 yellowish or reddish, with markings 



only on free surface 8. Thecaphora, p. 313. 



Spore-balls quite permanent; spores ad- 

 hering by folds or thickenings of 

 outer coat 9. Tolyposporium, p. 313 



